1. Field of the Invention
The present invention relates to an endotracheal intubation device that verifies placement of the endotracheal tube in the trachea, or windpipe, of a medical patient. More particularly, the endotracheal intubation device includes a suitable carbon dioxide absorbent that can physically and/or chemically interact with the carbon dioxide and a suitable visual indicator for detecting carbon dioxide absorption. By attaching the endotracheal intubation device to an endotracheal tube, placement of the endotracheal tube within the trachea, as opposed to within the esophagus, is verified by visually observing the color change of the chemical reagents, comprised of the carbon dioxide absorbent and the visual indicator. The incorrect placement of the endotracheal tube into the esophagus will not produce the visual color change because the carbon dioxide, present in the exhalations of the patient, is not available to contact the indicator treated carbon dioxide absorbent.
2. Description of the Prior Art
Endotracheal intubation is a routinely performed procedure, and one of the first techniques taught to the anesthesia trainee. Today the technique is performed by individuals having different backgrounds and levels of training in the operating suite, emergency room, intensive care unit, hospital ward and in the field.
However, the frequency of tracheal intubation in modern anesthetic practices belies its importance. Although endotracheal intubation is performed routinely in anesthesia, endotracheal intubation is a dangerous procedure and often does not receive the respect and attention it deserves. Anesthetic-related disability and mortality statistics indicate that unrecognized esophageal intubation, as opposed to endotracheal intubation, remains a problem, even among anesthesia personnel specifically trained in such a procedure.
Undiagnosed esophageal intubation continues to figure predominantly in anesthesia related morbidity and mortality. Birmingham, et al., in Anesth Analg., Vol. 65, page 886 to 891 (1986), reviews the various detection techniques for differentiating between endotracheal and esophageal tube placement, and found that most of the commonly utilized methods of verifying tube position have been shown to fail under certain circumstances.
The verification of correct tube placement within the trachea is a major problem for anesthesia and emergency personnel involved in endotracheal intubation. Both in surgical and emergency situations, intubation of the trachea often is necessary because normal airway protective reflexes have been lost, and therefore, tracheal intubation is required both to protect against aspiration of stomach contents and for ventilation.
However, because of the human anatomy, an attempt at endotracheal intubation may easily result in esophageal intubation. The anatomic proximity of the trachea and the esophagus facilitates inadvertent esophageal intubation during certain circumstances. For example the standard method of determining correct tube placement is visualization of the vocal chords. However, when the vocal chords cannot be visualized due to an atypical anatomy, excessive excretions or poor laryngoscopy technique by inexperienced personnel, verification of proper tube placement is essential. In addition, although the trachea may have been correctly intubated initially, during CPR (cardiopulmonary resucitation), involving relatively large chest movement of the patient, tracheal tube migration may occur with resultant extubation.
The overall result of esophageal intubation, or inadvertent endotracheal extubation, is the direct failure of both preventing aspiration of stomach contents and protecting the airway that provides ventilation for the patient. Therefore, the consequences are the aspiration of stomach contents, resulting in pneumonia, and the lack of ventilation, leading to brain damage and death unless endotracheal tube placement is quickly remedied.
A number of clinical tests, as discussed in the Birmingham et al. publication, are available to verify proper tube placement within the trachea. Among the several clinical tests discussed, actual visualization of the endotracheal tube passing the vocal chords is of primary clinical importance. However, neither this test nor any of the other clinical tests is fail-safe. It has been found however that the most definitive verification of correct tube placement involves an analysis for carbon dioxide gas including end-tidal carbon dioxide devices, in combination with mass spectometric carbon dioxide analysis.
During normal ventilation, oxygen inhalation provides oxygen for normal metabolic needs. When the metabolic by-products, predominantly carbon dioxide, are moved by exhalation, the end-tidal and mass spectometric techniques afford the medical practitioner both qualitative and quantitative evaluation of the exhaled gases, including the gas of primary concern, carbon dioxide.
At present, end-tidal carbon dioxide measurement is the most reliable means of determining proper tube position and is routinely employed when possible. However, the instruments utilized in these techniques are both extremely expensive and cumbersome in size. As a result, although Eichhorn et al., in JAMA, Vol. 256, Issue 8, pages 1017 to 1020, have deemed carbon dioxide analysis as one of the standards of medical care, many present-day operating rooms and clinics are not equipped with these carbon dioxide detection devices.
Several investigators have attempted to make verification of endotracheal tube placement both accurate and inexpensive. In Russian Pat. No. 157,059, an endotracheal device is disclosed that includes a whistle to verify that the tube is actually inserted in the trachea and not in the gullet. The whistle serves to give out a sound during exhalation and inhalation thereby confirming the presence of the tube in the trachea. The lack of a sound indicates that the tube has been placed within the esophagus as opposed to the trachea. However, this device has several drawbacks including sound generation by stomach gases, therefore giving a false positive placement of the tube; a device that can be clogged by secretions; a device and method that most likely is ineffective on a collapsed lung; a method that relies on the increase in thoracic gas pressure and not upon the analysis of an end-tidal gas, thereby requiring a disconnect from the ventilator or the stopping of cardiopulmonary resucitation to check for correct placement; and a device that is not reusable.
Gallagher, in U.S. Pat. No. 3,373,735, discloses a medical-surgical tube including a color change acid-based indicator, such that placement of the tube through the patient's nostrils into the patient's stomach can be verified. The placement of the tube within the stomach is verified by the color change of the indicator in response to the low stomach pH of approximately 1 to 2. Incorrect placement of the tube in the lungs will not produce the color change because the pH range in the lungs varies from approximately 7.45 to approximately 8.15. This device also suffers from serious drawbacks including the need for the sometimes absent secretions to cause a pH change, as opposed to analyzing an always present gas. In addition, incorrect results can occur because of secretions having a low pH being aspirated into the trachea or lungs. Other disadvantages include the possibility of clogging, the need to disconnect the ventilating device, the device is not reusable and the possibility of trauma due to the deep insertion of the device.
McCormick, in U.S. Pat. No. 4,431,005, discloses a method and apparatus for determining the position of a device within biological tissue by using an electromagnetic detecting device. This type of device suffers from the disadvantages of being fragile, expensive and stationary as opposed to portable. Furthermore, the method will only verify the height of the tube within the biological tissue, but not the depth of the tube within the biological tissue. Therefore, the method is potentially insufficiently accurate to distinguish between tracheal and esophageal placement.
British Pat. No. 345,672 discloses the use of an absorbent, containing a visual indicator, for detecting and for removing the water vapor in air or a gas. When the absorbent changes color, the absorbent is saturated with water vapor, indicating that fresh absorbent should be added to the device in order to keep the air or gas dry.
From the scope of the prior art, it is apparent that there is a need for a device that accurately and quickly verifies the correct placement of an endotracheal tube within the trachea both at the time of initial placement and at any time thereafter during treatment. Although some such devices are presently available, they are expensive, bulky and require trained personnel for proper usage. Therefore, for small hospitals, clinics, private physicians and emergency personnel, such as paramedics, it would be highly desirable to have an economical, reusable and portable device that quickly and accurately verifies correct endotracheal tube placement that can be used by either highly trained or relatively untrained medical personnel.